A protest sign opposing Hillside mine, near Ardrossan on South Australia's Yorke Peninsula

ABC News: Malcolm Sutton

Fears that dust from a planned mine on Yorke Peninsula could contaminate crops with low-level uranium and potentially travel as far as Adelaide have been raised by campaigners.

The YP Landholders Group said an estimated 3 million kilograms of dust produced annually by Rex Minerals' Hillside copper, gold and ore mine could include radioactive uranium and its decay products, called radon gas and radon daughters.

Chairman Stephen Lodge cited a joint paper written by United States doctor Dale Dewar that found "long-lived radioisotopes" from uranium mines could spread on surrounding land via dust and the water used for dust suppression.

Mr Lodge said Rex Minerals' own documents acknowledged the existence of uranium on the site near Ardrossan.

Key points

Rex Minerals to store 57ppm uranium

Safe guidelines to be reduced to 80ppm

Landholders want reassurances

Rex Minerals confident there's no issue

Full mine to proceed in 'stages'

Rex Minerals managing director Steve Olsen said uranium levels were well within regulated guidelines but acknowledged dust was a "valid and understandable" concern.

He said a range of dust suppression measures would be in place – including the shutdown of operations if necessary.

The firm has been given the go-ahead for a 2.4 kilometre-long, 1km-wide and 450m-deep open pit near Ardrossan that would extract 2 million tonnes of copper, 1.7 million ounces of gold and 44 million tonnes of iron ore over 15 years.

"Radon daughters are solids that stick to surfaces, such as dust particles," Mr Lodge said.

"Once uranium or copper or heavy metals are deposited on surrounding farmland they can be taken up by crops and pasture and then, of course, they enter the food chain.

"The Yorke Peninsula is renowned for strong north to north-westerly winds and, until farmers changed their practices, agriculture dust was regularly blowing 60 kilometres across the Gulf of Saint Vincent to Adelaide."

'Safe' levels of uranium under question

Mr Olsen, from Rex Minerals, said the site's tailing dams would contain uranium levels similar to the "host ore body of copper and gold", which averaged at about 57 parts per million.

"This is almost 75 per cent lower than the 200ppm limit where South Australian Environment Protection Authority (EPA) regulations take effect and, furthermore, the tailings will be encapsulated and buried within the waste rock facility," he said.

Dust is a valid and understandable concern.

Steve Olsen

The EPA plans to reduce that maximum from 200ppm to 80ppm in line with national guidelines.

In its Mining Lease Proposal Response Document released in February, Rex Minerals said concentrations of uranium on-site would be below the "potential revised licensing threshold of 80ppm for all but two years".

"It is Rex's intention to optimise the open pit schedule to ensure that uranium levels are reduced below 80ppm for all years," the document said.

Mr Olsen acknowledged that dust was a "valid and understandable" concern.

He said many people lived within kilometres of Hillside and many crops were grown nearby.

"Rex will employ a range of controls that will include the use of water trucks to keep haul roads moist, rehabilitating open areas, the stabilisation of soils stockpiles, along with a real-time monitoring system," Mr Olsen said.

But Mr Lodge said the level of uranium considered safe was constantly being downgraded and feared guidelines could be breached as a result.

"YPLOG is asking Rex to guarantee there will be no increase in background radiation, radioactive dust or radiation levels in rainwater tanks as a result of the Hillside operation," he said.

Business as usual and uranium concerns 'unwarranted'

Mr Olsen confirmed the company was moving ahead with its "ultimate plan" at Hillside but doing so in a more "staged manner", despite recently announcing a feasibility study into a smaller initial design.

He said the project's size, scale and staged options had been under consideration for some time and the announcement last week, which prompted the resignation of chief executive officer Mark Parry, was not made in response to approval conditions imposed by the SA Government.

"The many conditions would have been part and parcel of a mining licence anyway," he said.

"And just to be clear, Hillside is a copper-gold project.

"It has very low overall concentrations of uranium, which are comparable with the naturally occurring surface outcrops on the Yorke Peninsula (about 14ppm on average)."

Meanwhile University of Adelaide environmental scientist Professor Barry Brook said uranium was a heavy metal that would not travel far from the site.

He said it was possible for dust clouds to travel long distances but if naturally occurring low-level uranium was stirred up, it was more likely to fall in close proximity to the mine with other heavy metals.

The metals were "too heavy" to be included with any dust that rose into atmosphere, he said.